In a stunning turnaround, Iran's supreme leader Ayatollah Ali Khamenei has ordered an investigation into claims of election fraud.

Iran's current President Mahmoud Ahmadinejad was been declared the winner in the country's national election Saturday, but many voters are outraged, accusing him of stealing the election.

Click play for comments from Cliff May of the Foundation for Defense of Democracies, following this report.

Angry protests have led Iran's religious leaders to approve an investigation of the outcome.

Khamenei told the powerful Guardian Council to examine the allegations of widespread vote rigging. He previously welcome the election results, saying it was a 'divine assessment.'

Ahmadinejad's apparent win led to outrage and violent protests in the streets of Tehran over the weekend, with many saying the election was stolen. The riots were some of the worst opposition demonstrations to hit Iran since the Islamic revolution 30 years ago.

"It's a good feeling to see the people still have some courage left in them, when they feel like they're cheated," one protester said.

"It's been rigged. They've changed all results for themselves, and it's been a charade," another said.

The riots erupted shortly after Iran's Interior Minister announced that the incumbent, Ahmadinejad, had won a landslide victory with nearly 63 percent of the vote. His closest rival, Mir Hossein Mousavi, received only 33 percent in an election that polls had predicted would be tight. Reports even show Mousavi lost in his home town.

But Mousavi alleged widespread fraud, calling the election a "dangerous charade." By sunset, Mousavi supporters took to the streets and rooftops shouting "death to the dictator." There was hope among many Iranians, especially young people, that this election might bring greater social freedoms and a president who was less confrontational with the outside world.

Ahmedinajad supporters rallied in the thousands on Sunday to show their allegiance, defying accusations of vote-rigging.

"Everybody can accuse the other party of cheating. But the fact is that, ok, one million votes would be cheating, I accept that, two million, okay. But not 12 million," one Ahmadinejad supporter said.

The Iranian government responded with armor clad police, while Internet access to social networking sites was also clamped down.

Meanwhile, President Obama had called for an effort to renew ties between the two countries. The U.S. State Department, and other western capitals, have so far refused to accept the election results over concerns about their legitimacy.

"It sure looks like the way they're suppressing speech, the way they're suppressing crowds, the way in which people are being treated, that there's some real doubt about that," Vice President Joe Biden said.

During a press conference Sunday, Ahmadinejad was asked if he would take a more moderate line in his second term. He replied, "It's not true. I'm going to be more and more solid."

Ahmadinejad issued the world a warning: any country that dares attack Iran will face dire consequences.

"Whichever one of you bullying powers have the courage to threaten Iran, raise your hand so that this nation can cut your hand off," he said.